How to specify columns to be merged using pd.merge

TourEiffel 0
Viewed 26

Trying to use pd.merge , I don't understand how to specify the column we want to add in an other dataframe.

Is it possible?

Below is what I would Like to do :

DF1

index ID Style
0 1 a
1 21 z
2 7 e

DF2

index ID Name Date
0 1 ART 09-13-2022
1 21 DRAW 09-13-2022
1.1 7 GAME 09-13-2022
... 5 GAME 09-13-2022
115 8 GAME 09-13-2022

The output would be :

index ID Style Name
0 1 a ART
1 21 z DRAW
2 7 e GAME

I have tried :

Output = DF1.merge(DF2, on = 'ID', how='left')

Which works but it merge all column and not only the name column.

How can I specify 1 or several column(s) using merge? In this example, we need to specify that we want only Name column to be added to DF1.

pandas python
2 Answers

Slice DF2 to only keep the key(s) and the column(s) to add:

Output = DF1.merge(DF2[['ID', 'Name']], on='ID', how='left')

output:

    index   ID  Name
0       0    1   ART
1       1   21  DRAW
2       2    7  GAME
mozway0

You can change the columns associated to your dataframes within the merge itself, for example

Output = DF1.merge(DF2[['ID','Name']], on = 'ID', how='left')

This will only take the two columns you want into the merge and because 'Name' is an additional column it will join this onto DF1

Hillygoose0
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